As is known in the art, GaAs PHEMT's have exhibited superior low-noise and power performance compared to GaAs MESFET's for application to RF/microwave/milli-meter wave/millimeter-wave frequencies. This advantage has been achieved by bandgap engineering of GaAs, AlGaAs and InGaAs materials. Typically, depletion mode pHEMT transistors (which have a negative gate-source turn on voltage) are used in to amplify signals at RF/microwave/milli-meter wave frequencies. In some applications it is desirable to integrate digital functions on the monolithic circuits which incorporate high performance depletion mode rf transistors. For this, enhancement (E) mode transistors are used together with depletion (D) mode transistors to give the smallest circuits with the lowest power consumption and higher functionality for mixed mode applications. Enhancement mode transistors have a positive gate-source threshold voltage. It is difficult to introduce another material layer structure to implement the enhancement (E) mode PHEMT for monolithic integration of digital logic and RF circuits for mixed mode signal applications without disturbing the rf performance of the depletion mode PHEMT device.